A mobile station, also known as a User Equipment (UE), wireless terminal and/or mobile terminal is enabled to communicate wirelessly in a wireless communication network, sometimes also referred to as a cellular radio system. The communication may be made, e.g., between user equipment, between a user equipment and a wire connected telephone and/or between a user equipment and a server via a Radio Access Network (RAN) and possibly one or more core networks. The wireless communication may comprise various communication services such as voice, messaging, packet data, video, broadcast, etc.
The mobile station may further be referred to as mobile telephone, cellular telephone, computer tablet or laptop with wireless capability, etc. The mobile station in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another mobile station, a stationary entity or a server.
The wireless communication network covers a geographical area which is divided into cell areas, with each cell area being served by a network node, radio network node or base station, e.g., a Radio Base Station (RBS) or Base Transceiver Station (BTS), which in some networks may be referred to as “eNB”, “eNodeB”, “NodeB” or “B node”, depending on the technology and/or terminology used.
Sometimes, the expression “cell” may be used for denoting the network node itself. However, the cell may also in normal terminology be used for the geographical area where radio coverage is provided by the network node at a base station site. One network node, situated on the base station site, may serve one or several cells. The network nodes may communicate over the air interface operating on radio frequencies with any mobile station within range of the respective network node.
In some radio access networks, several network nodes may be connected, e.g., by landlines or microwave, to a Radio Network Controller (RNC), e.g., in Universal Mobile Telecommunications System (UMTS). The RNC, also sometimes termed Base Station Controller (BSC), e.g., in GSM, may supervise and coordinate various activities of the plural radio network nodes connected thereto. GSM is an abbreviation for Global System for Mobile Communications (originally: Groupe Spécial Mobile).
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), network nodes, which may be referred to as eNodeBs or eNBs, may be connected to a gateway, e.g., a radio access gateway, to one or more core networks. LTE is based on the GSM/EDGE and UMTS/HSPA network technologies, increasing the capacity and speed using a different radio interface together with core network improvements.
LTE-Advanced, i.e. LTE Release10 and later releases are set to provide higher bitrates in a cost efficient way and, at the same time, completely fulfil the requirements set by International Telecommunication Union (ITU) for the International Mobile Telecommunications (IMT)-Advanced, also referred to as 4G.
In the present context, the expressions downlink, downstream link or forward link may be used for the transmission path from the network node to the mobile station. The expression uplink, upstream link or reverse link may be used for the transmission path in the opposite direction, i.e., from the mobile station to the network node.
The increasing energy consumption of radio access networks has become more of an economic and environmental concern to the network operators. At the same time an ever increasing traffic demand requires more radio access resources to be utilised. Improving system and user throughput, while keeping the energy cost low, implies that future radio access networks should assure both spectral- and energy-efficiency. To this end, one solution approach that gains momentum for future networks is densification. However studies have showed that a plain network densification would significantly increase the overall energy costs.
Within 3GPP standards organisation densification refers to the deployment of large number of low power nodes (i.e., with small coverage area), which would provide an increasing number of radio resources closer to the mobile station. The availability of a large number of Radio Access (RA) resources belonging to one Radio Access Technology (RAT) induces interference which is associated with higher energy cost and requires spectrum sharing and interference coordination mechanisms. For operators that own legacy radio networks of multiple RATs, densification of radio accesses may be achieved by means of an integration of different RATs and Multi-Radio Access (MRA) selection mechanisms. This is easily accomplished as most mobile stations today support multiple frequency bands and radio access technologies. In addition, such a MRA densification would also provide non-interfering radio accesses, since different RATs operate at different frequencies. Therefore, there is currently a strong interest from operators and standardisation bodies in the integration of different radio access technologies to meet the increasing demand for wireless data traffic.
In a denser network it is beneficial to include both cellular and wireless LAN access technologies in base stations, and the mobile stations are likely to have interfaces for multiple RATs and base stations to connect over. So far, the integration of different cellular radio access networks are relatively tightly integrated, while integration between cellular and e.g. WLAN is implemented at high layers of the protocol stack, and not integrated in the access networks. However, the trend is that the integration is moving closer to the access networks, and for future networks an integration of the scheduling of multiple accesses is considered.
Multi-radio schemes have been investigated for various heterogeneous access networks consisting of various RAT combinations. The term heterogeneous networks, or HetNets, has been predominantly used for the single RAN case to denote a network environment that consists of a set of nodes that operate on the same spectrum with coverage overlap and different transmit power.
The term heterogeneous access networks refer to multi-radio networks that can co-operate to provide in a transparent way services to the mobile stations. In many cases this cooperation is realised in a form of efficient vertical handovers between the constituent RATs.
Split data flows between two communicating entities over more than one RAs has been performed to improve capacity. The problem is that as the data volumes increase more data needs to go through the receiver basebands of the small battery-driven mobile station devices. Targeting a 100× or 1000× times increase of the amount of traffic without doing anything about how many Joules per bit are spent, the battery of the mobile station will run out in just some few minutes. The energy consumption of different schemes for selection of the most suitable interfaces from an energy perspective during handover or coordinated transmission is thus an important topic. The energy consumed to transmit data to/from the mobile station depends on many factors pertinent to the implementation of the RAs and their radio interfaces. These factors comprises the data transmission and control overhead, the efficiency of multiple access and multiplexing scheme, deployed infrastructure and the transmit power used etc. Each RAT has its own energy consumption profile. Using multiple radio accesses for a user's data transmissions is associated to an additional energy cost, especially for schemes that improve robustness by introducing redundancy. The fundamental problem is how to select and use multiple radio accesses in an energy efficient way.
Finding an energy-efficient solution would be an advantage both at the network side, e.g., to reduce running costs, and at the mobile station devices to increase battery lifetime and improve the user experience.
Thus, the known prior art does not provide an efficient solution to directly control energy saving at the mobile station in a future heterogeneous and dense network.